A first oscillator is configured to be switchable between a disabled state and an oscillation state in which a first clock signal CLK1 having a first frequency is generated. A second oscillator oscillates at a second frequency that is lower than the first frequency, so as to generate a second clock signal. In (i) a power transfer phase in which electric power is transmitted to a wireless power receiving apparatus, a controller instructs the first oscillator to oscillate, and generates a first pulse signal for controlling a driver according to the first clock signal. In (ii) a selection phase in which the presence or absence of the wireless power receiving apparatus is detected, the controller generates a second pulse signal for controlling the driver at a predetermined time interval, which is measured based on the second clock signal, and during which the first oscillator is set to the disabled state.